The present invention relates to an apparatus for extracting milk from a breast, of the type described in the preamble to claim 1.
The present invention also relates to a pump unit for an apparatus for extracting milk from a breast, of the type described in the preamble to claim 13.
As is well known, apparatuses for extracting human breast, so-called breast pumps, generally comprise a kit for collecting the milk connected to an aspirating pump.
Typically, the collection kit comprises a rigid cup provided with a flexible inner coating and able to receive a breast, a container for collecting the milk connected to the cup and a second end connected to the aspirating pump.
The vacuum generated by the pump is of the pulsated type and it determines a suction on the breast within the cup, extracting the milk which thus flows within the coating and then slides into the collecting container.
In accordance with a first prior art, there are breast pumps provided with an electromechanical aspirating pump.
An important drawback of the first prior art is that the presence of an electromechanical pump does not allow to use the breast pump in the absence of a source of electrical energy, be it the electrical mains or a battery.
To overcome this drawback, breast pumps provided with a manually operated pump have been developed.
In accordance with a second prior art, there are breast pumps that comprise s kit for collecting the milk connected to a manually operated pump unit.
Generally, the kit for collecting the milk comprises a rigid cup, in whose interior is inserted a flexible coating, shaped in substantially complementary fashion to the inner surface of the cup.
The cup and the coating are able to receive at least one portion of a breast and its nipple and they are connected to a container for collecting milk.
Generally, the pump unit comprises a piston slidably inserted in a cylinder communicating with an aspiration conduit connected to the flexible coating. The head of the piston, moving with alternating motion within the cylinder between two operating positions that define different volumes of the cylinder, produce a cyclic aspirating and thus generates a predetermined degree of pulsating vacuum degree within the flexible coating.
Some breast pumps, instead of a normal piston, use a membrane piston that comprises an elastic membrane connected to the lateral walls of the cylinder and fixed on the head of the piston.
Note that, both in the case of a membrane piston, and in the case of a traditional piston, the alternating motion of the piston is activated by mechanical means connected to a stem of the piston itself and included in the pump unit.
In particular, said mechanical means generally comprise a lever with its fulcrum on a support structure, said lever having a first end connected to the stem of the piston and a second end that can be gripped by a user, in such a way that to an alternating rotation of the lever around an axis passing through the fulcrum corresponds and alternating motion of the piston within the cylinder.
Depending on the dimensions of the lever and on the position of the fulcrum, the ratio between the stroke of the piston and the travel of the lever is pre-set and constant.
An important drawback of the breast pumps provided with a manually operated pump assembly and constructed in accordance with the second prior art is the impossibility of varying the degree of vacuum generated by the piston. Since the ratio between the stroke of the piston and the travel of the lever is precept, the degree of vacuum generated by the pump unit is also pre-set.